Synthesis, structures, and optical and electrochemical properties of benzoporphycenes.

The first facile syntheses of free-base di- and tetrabenzoporphycenes and their metal complexes are reported, based on retro-Diels-Alder reactions of the corresponding bicyclo[2.2.2]octadiene-fused porphycenes, prepared by McMurray coupling of alpha,alpha'-diformyldipyrrole. The photophysical and electrochemical properties are analyzed based on UV/Vis absorption, magnetic circular dichroism (MCD), and fluorescence emission, lifetime and quantum yield measurements, cyclic and differential pulse voltammetry (CV and DPV) and time-dependent DFT calculations based on B3LYP geometry optimizations. Benzoporphycenes are found to be prime candidates for future use in photodynamic therapy.